AC LED driver circuit

Patent metadata

Field	Value
Publication number	US-9844118-B1
Application number	US-201615362260-A
Country	US
Kind code	B1
Filing date	Nov 28, 2016
Priority date	Feb 2, 2016
Publication date	Dec 12, 2017
Grant date	Dec 12, 2017

Abstract

An LED driver circuit controls the currents through a plurality of strings of light-emitting diodes (LEDs), which are connected in series. Each LED string has an associated current regulator. The LED strings are connected between the voltage rail and a reference rail on the output of an AC-to-DC rectifier to receive an unfiltered rectified DC voltage. A first current regulator is active during a first voltage range of the DC voltage to provide a current of a first magnitude to a first LED string only. A second current regulator is active during a second voltage range to provide a current of a second magnitude to the first LED string and to a second LED string. A third current regulator is active during a third voltage range to provide a current of a third magnitude to the first LED string, to the second LED string and to a third LED string.

First claim

What is claimed is:

1. A light-emitting diode (LED) driver circuit comprising:
a rectifier circuit configured to receive an AC voltage and produce between a voltage rail and a reference rail a rectified DC having a sinusoidal magnitude during each half-cycle of the AC voltage;
at least a first LED string comprising a first plurality of light-emitting diodes (LEDs) and a second LED string comprising a second plurality of LEDs, the first LED string having a respective first terminal connected to the voltage rail and having a respective second terminal, the second LED string having a respective first terminal connected to the second terminal of the first LED string and having a respective second terminal;
a first current regulator having a respective first terminal connected to the second terminal of the first LED string and having a respective second terminal connected to the reference rail,
the first current regulator configured, when the rectified DC voltage has a magnitude within a first voltage range, to enable a first current having a first current magnitude to flow from the second terminal of the first LED string to the reference rail, the first current flowing through the first LED string and not through the second LED string; and
a second current regulator having a respective first terminal connected to the second terminal of the second LED string and having a respective second terminal connected to the reference rail,
the second current regulator configured, when the rectified DC voltage has a magnitude within a second voltage range that is non-overlapping with respect to the first voltage range, to enable a second current having a second current magnitude to flow from the second terminal of the second LED string to the reference rail, the second current flowing through the first LED string and through the second LED string,
wherein when the magnitude of the rectified DC voltage is increasing, the first current regulator disables the first current through the first LED string before the second current regulator enables the second current through the first LED string and the second LED string.

2. The LED driver circuit of claim 1 , wherein:
the first voltage range has a first voltage magnitude and a second voltage magnitude, the second voltage magnitude greater than the first voltage magnitude; and
the second voltage range has a third voltage magnitude and a fourth voltage magnitude, the fourth voltage magnitude greater than the third voltage magnitude, the third voltage magnitude greater than the second voltage magnitude of the first voltage range.

3. The LED driver circuit of claim 2 , further comprising:
at least a third LED string, the third LED string comprising a third plurality of LEDs, the third LED string having a respective first terminal connected to the second terminal of the second LED string and having a respective second terminal; and
a third current regulator having a respective first terminal connected to the second terminal of the third LED string and having a respective second terminal connected to the reference rail,
the third current regulator configured, when the rectified DC voltage has a magnitude within a third voltage range, to enable a third current having a third current magnitude to flow from the second terminal of the third LED string to the reference rail, the third current flowing through the first LED string, the second LED string and the third LED string, wherein the third voltage range has a fifth voltage magnitude and a sixth voltage magnitude, the sixth voltage magnitude greater than the fifth voltage magnitude, the fifth voltage magnitude greater than the fourth voltage magnitude of the second voltage range.

4. The LED driver circuit of claim 1 , wherein a lowest magnitude voltage in the second voltage range is greater than a highest voltage magnitude in the first voltage range.

5. The LED driver circuit of claim 4 , further comprising:
at least a third LED string, the third LED string comprising a third plurality of LEDs, the third LED string having a respective first terminal connected to the second terminal of the second LED string and having a respective second terminal; and
a third current regulator having a respective first terminal connected to the second terminal of the third LED string and having a respective second terminal connected to the reference rail,
the third current regulator configured, when the rectified DC voltage has a magnitude within a third voltage range, to enable a third current to flow from the second terminal of the third LED string to the reference rail, the third current flowing through the first LED string, the second LED string and the third LED string, wherein a lowest voltage magnitude in the third voltage range is greater than a highest voltage magnitude in the second voltage range.

6. The LED driver circuit of claim 1 , wherein the second current magnitude is greater than the first current magnitude.

7. The LED driver circuit of claim 6 , further comprising:
at least a third LED string, the third LED string comprising a third plurality of LEDs, the third LED string having a respective first terminal connected to the second terminal of the second LED string and having a respective second terminal; and
a third current regulator having a respective first terminal connected to the second terminal of the third LED string and having a respective second terminal connected to the reference rail,
the third current regulator configured, when the rectified DC voltage has a magnitude within a third voltage range, to enable a third current having a third current magnitude to flow from the second terminal of the third LED string to the reference rail, the third current flowing through the first LED string, the second LED string and the third LED string, wherein the third current magnitude is greater than the second current magnitude.

8. The LED driver circuit of claim 1 , further comprising:
at least a third LED string, the third LED string comprising a third plurality of LEDs, the third LED string having a respective first terminal connected to the second terminal of the second LED string and having a respective second terminal; and
a third current regulator having a respective first terminal connected to the second terminal of the third LED string and having a respective second terminal connected to the reference rail,
the third current regulator configured, when the rectified DC voltage has a magnitude within a third voltage range, to enable a third current having a third magnitude to flow from the second terminal of the third LED string to the reference rail, the third current flowing through the first LED string, the second LED string and the third LED string, wherein the second voltage range and the third voltage range are non-overlapping; and
when the magnitude of the rectified DC voltage is increasing, the second current regulator disables the second current before the third current regulator enables the third current.

9. The LED driver circuit of claim 1 , further comprising:
at least a third LED string, the third LED string comprising a third plurality of LEDs, the third LED string having a respective first terminal connected to the second terminal of the second LED string and having a respective second terminal; and
a third current regulator having a respective first terminal connected to the second terminal of the third LED string and having a respective second terminal connected to the reference rail,
the third current regulator configured, when the rectified DC voltage has a magnitude within a third voltage range, to enable a third current to flow from the second terminal of the third LED string to the reference rail, the third current

Assignees

• Universal Lighting Tech Inc

Inventors

• Xiong Wei
• Berry Travis L
• Davis Keith
• Radzinski Christopher

Classifications

• H05B45/48 Primary

  having LEDs organised in strings and incorporating parallel shunting devices · CPC title

• H05B45/46

  having LEDs disposed in parallel lines · CPC title

• H05B33/0827

  Electricity · mapped topic

• H05B33/0809

  Electricity · mapped topic

• H05B33/089 Primary

  Electricity · mapped topic